1. Field of the Invention
The present invention relates to a fluid-filled elastic mount used as an engine mount or body mount of a motor vehicle, for example.
2. Description of the Related Art
Conventionally, a mount shown in FIG. 5 has been known as one example of a fluid-filled elastic mount for supporting an engine of a motor vehicle. This mount includes a first mounting metal member 1a, a rubber elastic block 2a which is secured on its upper side to the first mounting metal member 1a and has on its lower side a cavity, a cylindrical metal member 3a which is secured to an outer periphery of the lower side of the rubber elastic block 2a, a bottomed cylindrical second mounting metal member 4a which is caulked against a lower part of the cylindrical metal member 3a to define with the rubber elastic block 2a a closed space 7a, a diaphragm 5a a peripheral end portion of which is held between the second mounting metal member 4a and the rubber elastic block 2a to divide the closed space 7a into a fluid-filled chamber 8a filled with a fluid L and an air chamber 9a filled with air, and a partition member 6a which partitions the fluid-filled chamber 8a into a main chamber 81a and an auxiliary chamber 82a and defines with the rubber elastic block 2a an orifice passage 65a interconnected with the main chamber 81a and the auxiliary chamber 82a.
The mount thus constructed is assembled to a motor vehicle by securing the first mounting metal member 1a and second mounting metal member 4a to an engine and vehicle body, respectively, with mounting bolts 13a and 45a.
High-frequency vibrations from the engine are effectively absorbed by the elastic deformation of the rubber elastic block 2a, and low-frequency vibrations such as engine shake are effectively absorbed by the fluid mass resonance action of the fluid L passing through the orifice passage 65a due to the volumetric change of the main chamber 81a and the auxiliary chamber 82a. The internal pressure of the auxiliary chamber 82a is absorbed by the elastic deformation of the diaphragm 5a to generate a pressure difference between the auxiiary chamber 82a and the main chamber 81a, which enables a smooth pass of the fluid L through the orifice passage 65a.
In the conventional mount, the molecular motion of saturated air inside the fluid L may be activated due to a long period use in a high-temperature atmosphere, and the cavitation may be generated when high-frequency vibrations are input, which cause the residue of bubbles in the fluid L. In this case, the residual bubbles may block a smooth pass of the fluid L through the orifice passage 65a not to effect the fluid mass resonance action, thus not exhibiting sufficient vibration damping characteristics.
As effective means of restraining the generation and residue of bubbles, it is well known to increase the internal pressure of the fluid L inside the fluid-filled chamber 8a (Japanese patent application laid-open No. Hei 2-85539). The above-described conventional mount is, however, unable to increase the internal pressure of the fluid L inside the fluid-filled chamber 8a sufficiently, because it has a diaphragm 5a adapted to separate the fluid filled chamber 8a from the air chamber 9a so that the fluid filled chamber 8a is defined in part by the diaphragm 5a of low rigidity.